1. Field of the Invention
The present invention to a method and apparatus for manufacturing a luminescent device such as a flexible-type organic electroluminescent device.
2. Description of the Related Art
Electroluminescent devices are divided into organic electroluminescent devices using organic material as light-emitting layers and inorganic electroluminescent devices using inorganic material as light-emitting layers.
An organic electroluminescent device is a light emitting device which makes use of a principle that when an electric field is applied to a charge combination of holes from an anode and electrons from a cathode, the holes and the electrons are injected into an organic electroluminescent layer and are recombined with each other to generate energy which excites molecules in the organic electroluminescent layer. When the molecules are returned from an excited state to a ground state, light is emitted from the organic electroluminescent layer. Such an organic electroluminescent device has been developed ever since C. W. Tang et al. published “Organic Electroluminescent Diodes”, Applied Physics Lett. 51(12), pp. 913-915, Sep. 21, 1987.
A first prior art organic electroluminescent device is constructed by a transparent insulating substrate, a striped transparent lower electrodes (anodes) made of indium tin oxide (ITO), for example, formed on the transparent insulating substrate, a light emitting layer formed on the lower electrodes, and striped upper electrodes (cathodes) formed on the light emitting layer. As occasion demands, a hole-injecting and-transporting layer is interposed between the lower electrodes and the light emitting layer, and an electron-injecting and-transporting layer is interposed between the light emitting layer and the upper electrodes, thereby to enhance the injection efficiency of carriers such as holes and electrons into the light emitting layer. As a result, light emitted from the light emitting layer is emitted from the bottom side of the device (see: the above-mentioned document).
A second prior art organic electroluminescent device is constructed by an insulating substrate, striped lower electrodes (anodes) formed on the insulating substrate, a light emitting layer formed on the lower electrodes, and striped transparent upper electrodes (cathodes) on the light emitting layer. Also in this case, a hole-injecting and-transporting layer can be interposed between the lower electrodes and the light emitting layer, and an electron-injecting and-transporting layer can be interposed between the light emitting layer and the upper electrodes. As a result, light emitted from the light emitting layer is emitted from the upper side of the device (see: D. R. Baigent et al., “Conjugated Polymer Light-emitting Diodes on Silicon Substrates”, Applied Physics Lett. 65(21), pp. 2636-2638, Nov. 21, 1994).
The light emitting layer, the hole-injecting and-transporting layer and the electron-injecting and-transporting layer are made of organic materials. Therefore, an organic electroluminescent layer is constructed by a single organic structure or a stacked organic structure formed by a light emitting layer, a hole-injecting and-transporting layer and an electron-injecting and-transporting layer.
The above-mentioned organic electroluminescent layer is formed by a vacuum evaporation method or an ink jet method.
In the vacuum evaporation method, a shadow mask having fine holes is placed on a substrate having lower electrodes, and then, organic material is evaporated thereon. Then, the shadow mask is removed to leave an organic material pattern on the substrate (see: S. Miyata, “Organic EL Element and its Industrial Frontier”, pp. 172-173, November, 1998). This vacuum evaporation method is suitable for organic material having a low molecular weight.
In the ink jet method, organic material immersed into solvent is ejected from nozzles on a substrate having lower electrodes, and then, the solvent is removed to leave an organic material pattern on the substrate (see: S. Miyata, “Organic EL Element and its Industrial Frontier”, pp. 185-186, November 1998). This ink jet method is suitable for organic material having a high molecular weight as well as organic material having a low molecular weight.
The above-described organic electroluminescent device having a solid type substrate such as a glass substrate is applied to display units of a personal computer, a television set and the like; however, organic electroluminescent devices having a flexible substrate have recently been developed (see: JP-A-8-96954). Such organic electroluminescent devices have an advantage in that the devices can be adhered to curved faces and have an excellent substitute for paper.
However, no methods and apparatuses for manufactucturing such flexible-type organic electroluminescent devices have ever been disclosed.